Concerning trees and ornamental shrubbery for parks and open spaces, it is not possible to give detailed directions here, beyond recommending, as in the case of roadside plantations, that, unless the work is to remain permanently in the charge of an experienced gardener, with the necessary appliances for the care and protection of the more delicate specimens, the arrangement and the selection should be confined to the more hardy and vigorous trees and shrubs which experience has shown to be adapted to the climate and soil of the locality.
For roadsides, and largely in parks and village greens, the world offers no tree that can compare in dignity and grace with the broad-spreading American elm; though, for the sake of variety, and for the sake of an earlier effect, many other trees may be added.
VILLAGE SANITARY WORK.
It is a recently recognized but an old and universal truth, that human life involves the production of refuse matters, which, unless proper safeguards are taken, are sure to become a source of disease and death. The danger is not confined alone nor chiefly to that element of household waste which is most manifestly offensive, but in almost equal degree to all manner of organic refuse. It is true that fæcal matters are often accompanied by the inciting agent of the propagation of infectious diseases. For convenience, and as indicating the more probable means for disseminating infection, we may call this agent "germs." It has not yet been demonstrated with scientific completeness that a disease is spread by living germs whose growth in a new body produces a corresponding disorder; but all that is known of the circumstances of infection, and of the means for preventing it, may be fully explained by this theory. Typhoid fever, cholera, epidemic diarrh[oe]a, and some other prevalent diseases, are presumed by the germ theory to be chiefly, if not entirely, propagated by germs thrown off by a diseased body. So far as these ailments are concerned, there is therefore a very serious element of danger added in the case of fæces to the other evil effects which are produced by an improper disposal of any refuse organic matter. That any one or all of these diseases can originate from the decomposition, under certain circumstances of fæcal matters, is not clearly determined. There is, however, good reason for believing that one common effect of the gases arising from improperly treated matters of this kind is to debilitate the human system, and so to create a disposition to receive contagion, or to succumb to minor diseases which are not contagious.
The same debilitating effect and the same injurious influences often result from the neglect of other organic wastes. The refuse of the kitchen sink is free from fæcal matter; but it contains, in a greater or less degree, precisely the kind of organic material which has gone to make up the more offensive substance. If its final disposition is such as to contaminate the water that we drink or the air that we breathe with the products of their decay, the danger to life is hardly less than that from the decomposition of fæcal accumulations.
It is proposed now to set forth, in the simplest way and without much discussion of principles (which may be studied elsewhere), the methods and processes by which village households and communities may be protected against the influences that come from an excess of soil-moisture, from damp walls, and from imperfect removal or improper disposal of organic filth.
We will assume that a village has a water supply sufficient to admit of the use of water-closets in all houses, and to furnish a good flushing for kitchen sinks, &c. A necessary complement of this work—indeed, it should properly precede it—is the establishment of a system of sewers by which all of this liquid outflow may be carried safely away. It would be out of the question in a small or scattered community, especially where roadways are unpaved, to establish any system which should include in its working the removal of surface water. The moment we undertake to make sewers of sufficient capacity to carry away the storm water of large districts, then we enormously increase the scale and cost of the work.
So far as the removal of house sewage alone is concerned, the work need by no means be very costly. If a tolerable inclination can be given to the line of sewers,—say a fall of one in two hundred,—a six-inch pipe will have a capacity quite up to the requirements of a village of two thousand inhabitants using one hundred gallons of water per day per head. It will, however, be safe to use a pipe of this size only when it is true in form and carefully laid, so that there shall be no retarding of the flow at the joints from the intrusion of mortar, or any other form of irregularity. Unless the joints are wiped quite smooth, the roughness remaining will serve as a nucleus for the accumulation of hair, shreds of cloth, and other matters which will hold silt and grease, and form in time a serious obstruction. Nothing smaller than six-inch pipe should be adopted for a street sewer. Unless the work is to be most carefully done, for all but the branch lines, for a population of five thousand, or less according to the fall of the sewer, it will be safer to use eight-inch pipes. These pipes must be laid with great accuracy as to grade and direction. All corners should be turned with curves of large radius and regular sweep, and with an additional fall to compensate for the increased resistance of curves. The weight of the pipe should not be supported upon the sockets (see Figure 3), partly as a question of strength, and partly because any irregularity of form or thickness of the socket would change the inclination of the sewer. The bottom of the trench being brought exactly to the required grade, let there be dug out a depression greater than the projection of the socket, the pipe resting upon its finished bottom for its whole length. (See Figure 4.) Too much care cannot be given to the thorough filling with cement of the space between the socket and the pipe inserted into it; the whole circle being well flushed and wiped, so that there may be no possibility of leakage.
